Department of Biochemistry and Cell Biology, Stony Brook University, 450 Life Science Building, Stony Brook, NY 11794-5215, USA.
Division of Neurosurgery, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229, USA.
Glycobiology. 2021 Sep 9;31(8):988-1004. doi: 10.1093/glycob/cwab033.
Peters plus syndrome, characterized by defects in eye and skeletal development with isolated cases of ventriculomegaly/hydrocephalus, is caused by mutations in the β3-glucosyltransferase (B3GLCT) gene. In the endoplasmic reticulum, B3GLCT adds glucose to O-linked fucose on properly folded thrombospondin type 1 repeats (TSRs). The resulting glucose-fucose disaccharide is proposed to stabilize the TSR fold and promote secretion of B3GLCT substrates, with some substrates more sensitive than others to loss of glucose. Mouse B3glct mutants develop hydrocephalus at high frequency. In this study, we demonstrated that B3glct mutant ependymal cells had fewer cilia basal bodies and altered translational polarity compared to controls. Localization of mRNA encoding A Disintegrin and Metalloproteinase with ThromboSpondin type 1 repeat 20 (ADAMTS20) and ADAMTS9 suggested that reduced function of these B3GLCT substrates contributed to ependymal cell abnormalities. In addition, we showed that multiple B3GLCT substrates (Adamts3, Adamts9 and Adamts20) are expressed by the subcommissural organ, that subcommissural organ-spondin ((SSPO) also known as SCO-spondin) TSRs were modified with O-linked glucose-fucose and that loss of B3GLCT reduced secretion of SSPO in cultured cells. In the B3glct mutant, intracellular levels of SSPO were reduced and BiP levels increased, suggesting a folding defect. Secreted SSPO colocalized with BiP, raising the possibility that abnormal extracellular assembly of SSPO into Reissner's fiber also contributed to impaired CSF flow in mutants. Combined, these studies underscore the complexity of the B3glct mutant hydrocephalus phenotype and demonstrate that impaired cerebrospinal fluid (CSF) flow likely stems from the collective effects of the mutation on multiple processes.
彼得斯综合征（Peters plus syndrome）的特征是眼部和骨骼发育缺陷，伴有孤立的脑室扩大/脑积水病例，由β3-葡萄糖基转移酶（B3GLCT）基因突变引起。在内质网中，B3GLCT 将葡萄糖添加到正确折叠的血小板反应蛋白 1 型重复（TSR）的 O 连接岩藻糖上。所产生的葡萄糖-岩藻糖二糖被认为可稳定 TSR 折叠并促进 B3GLCT 底物的分泌，其中一些底物比其他底物对葡萄糖的丢失更敏感。B3glct 突变鼠以高频率发生脑积水。在这项研究中，我们证明与对照相比，B3glct 突变的室管膜细胞基底体纤毛较少，翻译极性改变。编码 A 型血小板反应蛋白 1 型重复 20 （ADAMTS20）和 ADAMTS9 的 mRNA 定位表明，这些 B3GLCT 底物的功能降低导致室管膜细胞异常。此外，我们表明，多个 B3GLCT 底物（Adamts3、Adamts9 和 Adamts20）由正中旁下器表达，正中旁下器-（SSPO）也称为 SCO-连接蛋白（SSPO）TSR 用 O 连接葡萄糖-岩藻糖修饰，B3GLCT 缺失减少了培养细胞中 SSPO 的分泌。在 B3glct 突变体中，SSPO 的细胞内水平降低，BiP 水平升高，表明存在折叠缺陷。分泌的 SSPO 与 BiP 共定位，这提示 SSPO 异常的细胞外组装成 Reissner 纤维也可能导致突变体中 CSF 流动受损。综上所述，这些研究强调了 B3glct 突变体脑积水表型的复杂性，并表明受损的脑脊液（CSF）流动可能源于该突变对多个过程的综合影响。
